Relay control circuits



July 11, 1961 A. J. CROUCHMAN RELAY CONTROL CIRCUITS F'ldJl 10,158 \22 1e uy United States Patent 2,992,368 RELAY CONTROL CIRCUITS Alan John Crouchman, Enlield, England, assignor to Daystrom, Incorporated, Murray Hill, NJ., at corporation of New Jersey Filed July 10, 1958, Ser. No. 747,750 Claims priority, application Great Britain July 17, 1957 6 Claims. (Cl. 317-152) This invention relates to relay control circuits and is more particularly concerned with an improved arrangement suitable for use under conditions of severe vibration such as in aircraft.

Relays of high sensitivity, such as are necessary in many forms of control circuit, are usually affected by vibration and under conditions where the vibration is severe their operation tends to be erratic and unreliable. Relays of a more rugged type, on the other hand, while less prone to adverse afiect by vibration, are usually of insufiicient sensitivity for proper operation in many forms of control circuit.

One of the objects of the present invention is the provision of an improved circuit arrangement permitting the use of high sensitivity relays, such as relays of the moving coil type, under conditions of severe vibration.

' In an arrangement according to the present invention two relays each of the requisite high degree of sensitivity are associated with two relays of a more rugged type in a circuit arrangement in which each of the sensitive relays is arranged to control the initial operation of a related one of the more rugged relays and in which the operation of the latter thereafter serves not only to exercise the desired control function but also to provide for its own locking-in, the locking-out of the associated sensitive relay and the release from locking-out of the other sensitive relay which was imposed at, the preceding time of circuit operation by such other sensitive relay.

In order that the nature of the invention may be readily understood, one embodiment thereof will now be briefly described with reference to the accompanying drawings in which:

FIGURE 1 is a circuit diagram of the aforesaid embodiment of the invention and shown with the various parts in the non-energised condition.

FIGURE 2 is a circuit diagram of the arrangement shown in FIGURE 1 when in one of its two alternative controlling conditions, while FIGURE 3 is a circuit diagram of the embodiment shown in FIGURE 1 when in the opposite one of its two alternative controlling conditions.

Referring first to FIGURE 1, the circuit arrangement comprises two sensitive moving coil relays C and D. The moving coil system of the relay C has a double winding consisting of a control winding cc and a separate locking winding cl. The moving coil system of relay D similarly has a double winding consisting of a control winding do and a separate locking winding dl. Each moving coil relay C, D has the usual movable contact carried by the moving coil element, such movable contact co-operating with fixed contacts to form a contact pair as shown at 01 and d1 respectively which is closed when the moving coil element is sufiiciently rotated in one direction and opened when rotated in the other direction. Two further relays A and B are provided, such relays having contact sets a1, a2 and b1, b2 respectively. Such further relays A and B are of a type more rugged than but less sensitive than that of the relays C and D and may be of the normal electromagnet/ pivotal armature type.

One terminal of the operating winding of each of the r gged relays A, B is connected to one, say the negative,

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busbar g2 of a direct current supply circuit while the opposite terminal of the operating winding of relay A is connected to the moving contact of the contact set b1 of the rugged relay B and is also connected to one end of the locking winding cl of the sensitive relay C. The opposite terminal of the operating winding of rugged relay B is connected to the back contact of the contact set al of the rugged relay A and is also connected to one end of the locking winding dl of the sensitive relay D. The moving contact of the contact set al of rugged relay A is connected to the other, say the positive, busbar g1 of the aforesaid current supply circuit, which busbar g1 is also connected through resistor R to one contact, conveniently the fixed contact, of each of the pair of controlled contacts c1, d1 of the sensitive relays C and D. The opposite end of the locking winding cl of the sensitive relay C is connected to the opposite, e.g. the moving, contact of the contact pair c1 of such relay and also by way of resistor Y to the aforesaid negative busbar g2 of the current supply circuit. The opposite end of the locking winding dl of the sensitive relay D is similarly connected to the opposite, moving, contact of the contact pair d1 of such relay D and also through a resistor X to the same negative busbar g2 of the current supply circuit.

The control windings cc and dc of the sensitive relays C and D respectively are connected in series and across the source of input control signals shown applied by way of the leads s1 and s2. The further contact sets a2 and b2 of the rugged relays A and B are not shown as connected into any circuit but are available for control of any required form of output circuit or circuits.

FIGURE 1 shows the circuit in the condition when no input current is made available on the busbars g1 and g2. When such supply current is made available on these busbars, the circuit assumes the condition shown in FIGURE 2. Current now flows from busbar g1 by way of the back contact of contact set al of rugged relay A through the operating winding of rugged relay B to the busbar g2, thereby operating relay B. Current also flows by way of the same contact set a1 through the locking winding dl of the sensitive relay D and resistor X to the busbar g2. This current flow is in a direction within winding dl which operates to move the contacts of the contact pair d1 apart. These control contacts are accordingly now wide open and free from any risk of accidental engagement under vibration conditions. Such sensitive relay D is now effectively inoperative and will remain in this locked-01f condition until the throw-off current passing through winding dl is removed.

When, with the circuit in the condition as shown in FIGURE 2, the input control signal injected over leads s1, s2 into the serially connected control windings cc, do of sensitive relays C and D is of correct polarity and is of sufiicient amplitude to close the contact pair 01 of the sensitive relay C, current then flows from the positive busbar g1 through resistor R, .the now-closed contact pair (:1, the locking winding cl of the sensitive relay C and the operating winding of the rugged relay A to the negative busbar g2. The direction of flow of this current in the winding cl is such that it causes the moving contact of the contact pair c1 of the sensitive relay C to lock in hard against the associated fixed contact and the rugged relay A is accordingly fully energised to cause reliable operation thereof to change over the position of its contact sets a1 and a2. By the resultant opening of the circuit through the back contact of set al this change-over operation then removes current from the operating winding of the rugged relay B and the locking winding dl of the sensitive relay D and the rugged relay B thereupon releases to reclose the back contact of contact set b1.

3 The closure at the back contact of contact set b1 causes current to flow from the positive busbar g1 through the now-operated contact set al, the released contact set b1 and the operating coil of the rugged relay A to the busbar g2 thereby locking-in relay A in its operated state. At the same time current also flowsthrough the locking winding cl of the sensitive relay C and resistor Y to the busbar g2. This current is in the reverse direction to that of the previous locking-in current applied to this winding and accordingly causes the moving contact of the sensitive relay C to move as far as possible in the direction away from the associated fixed contact of the contact pair 01 whereby such contacts are thrown widely open and risk of accidental contact closure due to vibration is completely removed. The relay C is now effectively inoperative and will remain in such locked-01f condition until the throw-01f current through locking winding cl is removed. By the same operation, however, the throw-ofi current in the looking winding dl of the sensitive relay D has been removed due to the circuit opening at the back contact of the contact set al of the now-operated rugged relay A. The sensitive relay D is accordingly now free to respond to the appropriate current conditionsof the input control circuit on leads s1 and s2. The circuit is now in the condition shown in FIGURE 3.

When the signal injected by way of leads s1, s2 is of the correct amplitude and polarity to cause the moving contact of the contact pair d1 of the sensitive relay D to close with the associated fixed contact, current now flows from the busbar g1 through resistor R, the now-closed controlled contacts of pair d1 of the sensitive relay D, the locking winding dl of such relay D and the operating winding of the rugged relay B to the busbar g2. This causes the contacts of the pair d1 of the sensitive relay D to be locked in hard and thereby ensures that the operating winding of the rugged relay B is fully energised to cause reliable operation of such rugged relay. This operation of the rugged relay B opens the circuit previously established through the back contact of the contact set b1 whereby the operating winding of the rugged relay A is now dc-energised and the previous throw-off current through the locking winding cl of the sensitive relay C is removed. The resultant change-over of position of the contact set a1 then closes a locking circuit from the busbar g1 through the back contact of contact set a1 and the operating winding of the rugged relay B to the busbar 0. thereby locking-in such relay B. At the same time current also flows through the locking winding dl of the sensitive relay D and the resistor X to the busbar g2 thereby reversing the direction of current flow in such locking winding and causing the moving contact of the sensitive relay D to be moved as far as possible away from the associated fixed contact of the pair d1 of such relay to render such contacts immune from any adverse effect of vibration. The circuit is now reversed back to the condition shown in FIGURE 2 in readiness for the next change of input signal conditions in the opposite sense as already described.

I claim: 1. A relay control circuit arrangement comprising a first sensitive moving coil relay and a second sensitive moving coil relay, each of said relays being susceptible to vibration and having a movable contact carried by its moving coil, cooperating with a fixed contact, a control Winding and a locking winding, said movable and fixed contacts being engaged when the moving coils are rotated in one direction and disengaged when said coils are rotated in the other direction, a first rugged relay and a second rugged relay, each of said rugged relays having a control winding, movable and fixed contacts, and being less susceptible tovibration than said moving coil relays, means connecting one terminal of the control winding of each of the rugged relays to the first busbar of a direct current supply and the opposite of said terminals of each of said rugged relays to one of the contacts of the other and to one terminal of the locking winding of the sensitive relay of corresponding number, means connecting the other contact of one of said rugged relays to the second busbar of said supply, means con-- necting said second busbar to one contact of each of the pair of controlled contacts of said moving coil relays, means connecting the other terminal of the locking winding of the first moving coil relay to the other of its controlled contacts and also to the first busbar, means connecting the other terminal of the locking winding of the second moving coil relay to the other of its controlled contacts and also to the first busbar, and means connecting the control windings of the moving coil redays across a source of input control signals.

2. A relay control circuit arrangement as claimed in claim 1, wherein said double windings of said moving coil systems are completely separated from one another electrically and wherein one of such windings of each system is connected to be energised only by input control current and the other winding by current from a local current supply source.

3. A relay control circuit arrangement according to claim. 2, wherein said separate windings energised by the input control current are connected in series.

4. A relay control circuit arrangement according to claim 2, wherein the other winding of each of said double wound moving coil systems is connectedin parallel with the operating winding of the related rugged type relay.

5. A relay control circuit arrangement according to claim 4, in which the parallel circuit connection of said other moving coil system winding across said rugged relay operating winding includes a series resistor.

6. A relay control circuit arrangement according to claim 5', in which first circuits for the supply of current from said local source respectively to said parallel connected windings of said moving coil systems and the related rugged relays are each arranged to be by way of the controlled contacts of the related high sensitivity relay and in which second circuits for supply of current from such local source to said same parallel connected windings respectively are arranged to be by way of contacts controlled by the opposite unrelated rugged relay whereby the direction of current flow in said moving coil system winding can be reversed to throw open the controlled contacts of the related high sensitivity relay.

References Cited in the file of this patent UNITED STATES PATENTS 

